Electronic tube and apparatus employing same



March 28, 1939. o. T. M ILVALNE ELECTRONIC TUBE AND APPARATUS EMPLOYING SAME Filed July 9. 51934 [N VENTOR -u m w 35.-

Patented Mar. 28, 1939 PATENT OFFICE ELECTRONIC TUBE AND APPARATUS EIVIPLOYING SAME Oran T. Mcllvaine, St.

Charles, 111., assignor to The Mcllvaine Patent Corporation, St. Charles, Ill, a corporation of Delaware.

Application July 9, 1934, Serial No. 734,353

Claims.

This invention relates to electronic tubes and apparatus for employing same, as for example, radio receiving and transmitting apparatus and it constitutes in part a continuation of my co- 5 pending application Serial Number 209,281 filed July 29, 1927, for Electronic tube, which application matured into U. S. Letters Patent 1,965,849 011 July 10, 1934.

The present invention has for its object the provision of improved forms of electronic tubes for radio work and the utilization of such tubes in new and novel apparatus and circuits.

With these and other objects in View, the invention consists in the novel construction, arrangement and combination of parts, hereinafter illustrated and described in some of its embodi ments in the accompanying drawing, and particularly pointed out in the appended claims.

In the drawing, Figure 1 is a vertical sectional view of a tube illustrating some of the features of the invention; and Figure 2 is a diagrammatical view of a radio receiving set employing tubes utilizing the general principles of construction of the tubes shown in Figures 1 and 2.

The tube shown in Figure 1 comprises a transparent envelope, preferably made of glass, having an inner concentric wall part I fused to the outer wall part 2 at 3. This tube has a light-sensitive electrode or photo-cathode 4, on the inner surface of its outer wall 2, an anode element 5 in the form of a coarse mesh screen and a grid element 6 interposed between the cathode and anode. A lamp 7 is provided for connection in the circuit, in which the tube is used, and this lamp is preferably of the general type of which the neon lamp is an example. The light of a lamp of this sort will follow every fluctuation of its supply current or that of the incoming radio signals when the tube is used in a radio receiver. The light of the lamp 1 is used to actuate the photo-cathode 4, thereby effecting the amplification of radio signals without the use of a transformer or any other coupling means. External conductors 9, I0, I! and I2 are connected to the photo-cathode l, the grid 6, the lamp 1 and the anode 5, respectively.

The principal advantage derived from the use of a tube of this type, as will be explained in detail later, is that of being able to couple one stage of amplification to a following stage by means of a light beam which can fluctuate at any frequency, thereby eliminating transformers, capacitors, resistances and all other forms of coupling between stages heretofore employed and considcred as necessary. In the prior art radio devices,

amplification per stage is limited by the effect of oscillation between stages to the energy being fed back and forth through the coupling device, so that the maximum amplification possible in a multi-tube set today, very seldom exceeds an amplification of 30 per stage.

In the eight-tube superheterodyne set of a few years ago, an amplification of 3000 or more was considered very good. With modern tubes, an amplification of 1000 to 1500 per tube is very common. However, as stated before, in a multitube set this extreme amplification cannot be used due to inter-stage coupling which produces oscillation, thereby making the set inoperative.

By use of the arrangement disclosed herein, a much higher degree of amplification can be attained with a lesser number of tubes than previously used. The reason this is possible is due to the fact that each stage may be completely isolated in a metal box, having absolutely no connection from one stage to the other, with the exception of the beam of light which travels from one stage to the photo-sensitive element of the next succeeding stage. This permits amplification of the useful energy through successive stages and at the same time it prevents any currents feeding from one stage back to the other stage, thereby causing oscillation.

The employment of the tubes and lamps of the types herein shown, permits the construction of a superheterodyne receiver by merely oscillating a certain stage at the desired frequency and shining the fluctuating light from a lamp in circuit with the oscillating stage on the photo-cathode of the tube in which it is desired to have the mixing take place. By this method, any current of a desired frequency can besuperimposed into the main stream without any ill cifects from parasitic oscillations or extraneous currents which might occur if electromagnetic coupling were used, which is the common method being employed today in most types of modern receivers.

Figure 2 shows a circuit which may be in the form of a radio receiver set of three stages, em ploying light beams in the amplification of the signals or the pulsations of a source of high frequency current. The letters A, B and C are used to indicate the individual tubes used in the three 0 accordance with such signal and constitutes a source of high frequency radiations.

The light from the lamp 25 is collected by a lens 26 and directed to a photo-cathode 21. The photo-cathode may be in the form of a spherically shaped glass shell with a light transparent sensitized coating of a material such as caesium which emits electrons when subjected to light so that the cathode can be operated by light directed at either its front or its rear side. The electron emission thus induced at the photo-cathode influences the charge on a grid 28 to which it is connected and which in turn controls the electron fiow from both the photo-cathode 21 and a hot cathode 3|] to an anode 3|. The anode 3| controlsa second gas discharge lamp 32, the light from which is directed through a lens 26 to the photo-cathode 21 of the next stage which is electrically isolated from the first by means of a metal box, the walls of which are indicated by the numeral 29 and a similar box is provided for each of the other stages of the set.

Suitable connections are provided between the elements of the tube and thebatteries 33 and 34. A non-inductive resistance 35 and either an inductive or a non-inductive resistance 36 is connected in series with the filamentary cathode 30 and the grid 28 respectively. Instead of forming thephoto-cathode from a transparent glass shell having a transparent sensitized coating thereon, thesame might be formed from metal and by reversing: the position of either the tube or the lamp of' each stage, the light of each lamp could'be directed against the concave face of the photo-cathode as is done in the first stage of the set.

The lamps and tubes shown in the three stages of the upper part of Figure 2, are substantially identical and the coupling of one stage to the next is effected simply by the useo-f a light beam as indicated by the dotted lines in Figure 2 of the drawing, each step operating substantially in the mannerdescribed in connection with the operation of the tube A, except that at the final stage the lamp may be replaced by a transformer 3! or the winding of a loud speaker.

When it is desired to modulate two different high frequency currents or two signals coming from different stages and oscillating at different frequencies, the same may be done by shining the light from such two different stages onto the photo-cathode of another stage. These signals or currents can be mixed in the main circuit at any desired stage thereof and one method of eifecting such result will be described in detail presently.

- The lower part of Figure 2 isintended to illustrate diagrammatically any source of high frequency current and it includes in circuit therewith any suitable light source, as for example a hot'cathode type of lamp 38 having a heater 40, a cathode 4i, and an anode 42. The light from this lamp is. caused to pulsate by the plate current from the triod-anode 43of an amplifier tube D, having a grid 45 connected to a transformer 44 which in turn may be connected to the anode 43 or otherwise to complete thecircuit between the lamp and the tube D. Suitable batteries 46 and 41 and connected'to the filament 48 and plate or anode 43 of'the tube D and another battery 50 may be provided for heating the filament 40 of the lamp 38;

"The light emitted by the lamp passes through a lens 5! and then through an optical wedge 52 of crown and flint glass which bends the rays without dispersion and directs them to the photocathode of the tube C. For convenience, the light is introduced into the last stage of the set. The various stages of the set are shown as being battery-operated, merely to indicate a source of potential. However, as is Well understood in the art, these stages could be operated by alternating current by means of a proper kind of power supply and filter in each stage. The arrangement shown in Figure 2 is intended to illustrate as simply as possible the manner in which the different stages of the circuit are coupled to each other and for the sake of simplicity, many of the conventional and well understood elements of a modern receiver have been omitted from this figure.

It is to be understood that the tube shown in Figure 1 could be used in place of the tubes used in Figure 2, as proposed in my patent referred to earlier herein. The-replacement of the tubes of Figure 2 by tubes-such as the one shown in Figure l would involve no changes in the circuit other than the elimination of the connections for the heated filaments 30 and the location of the lamps in position to effect electron emission by the photo-cathode 4. The tubes illustrated in Figure 2 are preferred, however, because the greater degree of amplification which they make possible" through the utilization of the electron emission of both a heated filament and a light sensitive cathode.

It should be noted that each stage is entirely separate from the other and there is no connecting link between various stages, and for this reason it is impossible to have interfering disturbances fed from one stage to the other. In this way, enormous amplifications running as high as 1500 to 2000 per stage can be obtained Without having any interfering oscillations due to interstage coupling as the useful energy is fed from one stage to the other by a light beam which cannot in any way couple parasitic currents from the following stage to the preceding stage.

Furthermore, it is to be understood that the particular forms of electronic tubes and apparatus shown and described, and the particular procedure set forth are presented for purposes of explanation and that various modifications of said apparatus and procedure can be made without departure from this invention as described in the appended claims.

Having thus described my invention, what I claim is:

1. The combination with a source of light in the form of a gaseous glow discharge lamp and means for causing the same to fluctuate, of an amplifier tube comprising an anode and grid and an associated cathode adapted and positioned to emit electrons under the influence of the light of said lamp and a transparent envelope for enclosing said anode, grid and cathode, and a second gaseous glow discharge lamp in circuit with the anode of said tube and constituting a variable source of light the intensity of which is amplified by said tube and varies in accordance with the fluctuations of said first named lamp by reason of the impingement of the light thereof onto the cathode of said tube and the fiow of electrons to said anode from said cathode.

2. The combination with a source of light in the form of gaseous glow discharge lamp and means for causing the same to fluctuate, of a source of electrical energy therefor and an amplifier tube comprising an anode and grid and an associated cathode adapted and positioned to emit electrons under the influence of the light of said lamp and a transparent envelope for enclosing said anode, grid and cathode, and a second gaseous glow discharge lamp in circuit with the anode of said tube and constituting a variable source of light the intensity of which is amplified by said tube and varies in accordance with the fluctuations of said first named lamp by reason of the impingement of the light thereof onto the cathode element of said tube and the flow of electrons to said anode from said cathode.

3. The combination with a source of light in the form of a gaseous glow discharge lamp and means for causing the same to fluctuate, of an amplifier tube comprising an anode, a filamen tary cathode, a grid and a photo-cathode adapted and positioned to emit electrons under the influence of the light of said lamp and a transparent envelope for enclosing said anode, filamentary cathode, grid and photo-cathode, and a second gaseous glow discharge lamp in circuit with the anode of said tube and constituting a variable source of light the intensity of which is amplified by said tube and varies in accordance with the fluctuations of said first-named lamp by reason of the impingement of the light thereof onto the photo-cathode of said tube and the flow of electrons to said anode from both said photo-cathode and said filamentary cathode.

4. In a radio-receiving apparatus having a plurality of stages for the receiving and the mixing and amplification of pulsating electrical currents of different frequencies, the method of amplifying and mixing such currents which comprises the steps of producing light impulses corresponding to the electrical pulsations of an incoming radio signal at one stage of the receiver, transforming such light impulses into corresponding electrical pulsations and amplifying the same at another stage, transforming such amplified electrical pulsations into amplified light impulses, and utilizing light impulses of a fixed frequency to generate an electrical current of the same frequency at another stage whereat the amplified light impulses are transformed into electrical impulses and modulate the current at such stage in accordance with the incoming radio signal.

5. In a radio-receiving apparatus having a plurality of stages for the receiving and the mixing and amplification of pulsating electrical currents of difierent frequencies, the method of amplifying and mixing such currents which comprises the steps of producing light impulses corresponding to the electrical pulsations of an incoming radio signal at one stage of the receiver, transforming such light impulses into corresponding electrical pulsations and amplifying the same at another stage, transforming such amplified electrical pulsations into amplified light impulses, util'ming light impulses of a fixed frequency to generate an electrical current of the same frequency at another stage whereat the amplified light impulses are transformed into electrical impulses and modulate the current at such stage 'in accordance with the incoming radio signal,

ORAN T. MCILVAINE. 

